FreeBSD bhyve VM on ZFS - 2023-08-06

The default disk type when using vm-bhyve is a file on the filesystem. Changing it to ZFS is quite easy.

Setup

Assuming the following configuration after installing vm-bhyve in /etc/rc.conf:

vm_enable="YES"
vm_dir="zfs:zroot/vms"

And a vm-bhyve mountpoint set to /usr/local/vms.

Howto

First we create a new VM. In this guide we use the name testvm.

vm create -t alpine -c 1 -m 2G testvm

Meaning:
-t alpine: use the alpine template
-c 1: one core
-m 2G: 2GB of memory

Delete the disk image file as we will not need it.

rm /usr/local/vms/testvm/disk0.img

Create a ZFS dataset underneath the dataset used for the VM:

zfs create -V20G -o volmode=dev zroot/testvm/disk0

Meaning:
-V20G: Create dataset with a size of 20GB
disk0: Name of the dataset which needs to be referenced in the configuration file

Alter the configuration in /usr/local/vms/testvm/testvm.conf to look like this:

loader="uefi"
cpu="1"
memory="2G"
network0_type="virtio-net"
network0_switch="public"
disk0_type="nvme"
disk0_dev="zvol"
disk0_name="disk0"

This is it. Now you can start installing an OS as you would normally do via vm install testvm <iso>.

If you plan on installing your OS via a GUI, you might want to add the following to you configuration to be able to connect via VNC to your VM (requires UEFI!):

xhci_mouse="yes"
graphics="yes"
graphics_res="800x600"